Large scale earth moving and/or grading operations, such as cutting and cleaning ditches or trenches, are typically accomplished by large vehicles, such as a tracked vehicle such as a bulldozer, or a wheeled vehicle like a grader. Typically, each of those vehicles has an earth moving blade which is capable of a certain range of movement. For instance, the bulldozer has a front blade which is capable of vertical movement for cutting and grading operations directly in front of the vehicle. The grader, on the other hand, has a blade located beneath the carriage of the vehicle which may be oriented at particular angles but which may not be raised or lowered vertically to any substantial extent. Such a blade accomplishes certain cutting and grading operations beneath the vehicle.
With these conventional blades, however, it is not possible to do cutting or cleaning along a vertical side of a trench adjacent the vehicle, or to do grading above or below the vehicle. Also it is not possible to cut a ditch along side the vehicle. Hence, conventional blades are rather limited in their application.
Certain special purpose attachment blades are known, however, which provide increased capability for such vehicles. One blade in particular which is in use attached to the front side of a bulldozer is referred to as a slope board. With the slope board, the blade may be positioned at a selected angle in a plane transverse to the vehicle and may also be moved to a selected position in a longitudinal plane relative to the vehicle. The slope board attachment permits a bulldozer to clean and cut the sides of a trench in which the vehicle is moving. However, such a blade cannot be used for cutting or cleaning below the vehicle, and is also limited in its upward reach. Furthermore, some functions such as finishing off a ditch, and cutting a ditch under adverse weather conditions are not possible with the slope board. The dirt removed by the blade also falls beneath the vehicle, which is disadvantageous. Still further, the use of the slope board on a bulldozer limits the effectiveness of the front blade because of the front end weight and side loading added by the slope board and the increase in the effective overall width of the vehicle. Thus, the use of the slope board limits the total capability of the vehicle.
Other specialized accessory blades for particular purposes are also known, some of which are adapted specifically for use with a tracked vehicle such as a bulldozer and others for a wheeled vehicle such as a grader.
However, there is no known bulldozer or grader blade which will permit the use of a vehicle like a bulldozer (for instance) in its conventional configuration, while providing the increased capability of performing a multitude of cutting, cleaning and grading functions, including operations on ground above and below the vehicle. It is desirable to have a single blade attachment which may be moved into a wide variety of positions relative to the bulldozer and which has a reach which extends both above and below the vehicle itself and a range of angles in both the horizontal and vertical planes relative to the vehicle.